This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. Primary support for the subproject and the subproject's principal investigator may have been provided by other sources, including other NIH sources. The Total Cost listed for the subproject likely represents the estimated amount of Center infrastructure utilized by the subproject, not direct funding provided by the NCRR grant to the subproject or subproject staff. Based on clinical, histopathological and serological similarities to human celiac disease, we recently established the rhesus macaque model of gluten sensitivity. In this study, we further characterized this condition based on presence of anti-tissue transglutaminase 2 (TG2) antibodies, increased intestinal permeability and transepithelial transport of a proteolytically resistant, immunotoxic, 33-residue peptide from alpha-2-gliadin in the distal duodenum of gluten-sensitive macaques. Six rhesus macaques were selected for study from a pool of 500, including two healthy controls and four gluten-sensitive animals with elevated anti-gliadin or anti-TG2 antibodies as well as history of non-infectious chronic diarrhea. Pediatric endoscope-guided pinch biopsies were collected from each animal's distal duodenum following administration of a gluten-containing diet (GD) and again after remission by gluten-free diet (GFD). Control biopsies always showed normal villous architecture, whereas gluten-sensitive animals on GD exhibited histopathology ranging from mild lymphocytic infiltration to villous atrophy, typical of human CD. Immunofluorescent microscopic analysis of biopsies revealed IgG+ and IgA+ plasma-like cells producing antibodies that colocalized with TG2 in gluten-sensitive macaques only. Following instillation in vivo, the Cy-3-labeled 33-residue gluten peptide colocalized with the brush border protein villin in all animals. In a substantially enteropathic macaque with "leaky" duodenum, the peptide penetrated beneath the epithelium into the lamina propria. The rhesus macaque model of gluten sensitivity not only resembles the histopathology of CD but it also may provide a model for studying intestinal permeability in states of epithelial integrity and disrepair.